1. The Field of the Invention
The present invention generally relates to cellular telephone systems. More particularly, the present invention relates to methods and systems for attaching a watermark identifier to cellular signals in a cellular repeater system.
2. The Relevant Technology
In recent years, cellular (“cell” or “mobile”) telephones have dramatically increased in popularity. This increase in cell phone reliance places increased demand on network providers to provide reliable cellular signal coverage over a wider area. Use of cell phones in areas having a weak signal often results in dropped calls which can be annoying for the cell phone user and expensive for the wireless service provider. A loss of signal may occur for a number of reasons, including interference due to buildings or mountains, or an increase in distance between the cell phone and the base station. Therefore, a need exists to increase the reliability of signal coverage in a wireless network.
Attempts have been made to increase the reliability of cell phones through use of Cellular or Personal Communications Service (PCS) telephone signal boosters, also known as cellular network amplifiers and repeaters. Cellular network amplifiers are typically placed in relatively close proximity to cell phones, and serve the purpose of increasing the level of the signals being transmitted to and from the cell phones so that the cell phones can communicate with base stations that would otherwise be out of range.
There are a number of methods for repeating a cellular or PCS telephone signal into an area, such as inside a building, where the signal strength is insufficient. One such method is to mount an antenna on the outside of the building to receive the signal from a base station, amplifying the signal, and then reradiating the amplified signal into the interior of the building via an indoor antenna to one or more handsets. Similarly, signals from a handset within the building are received by the indoor antenna, amplified, and reradiated by the outdoor antenna back to the base station.
When a signal passes through such a repeater system, its level is increased. At the same time, however, the signal is also delayed by the cables leading from the outside antenna to the amplifier, from the amplifier to the inside antenna, and by various filters within the amplifier itself. The amplifier may affect the signal in other ways that may vary with each amplifier's parameters. These effects may disrupt certain system features and calculations performed by the base station. For example, if the filters of an amplifier are narrow in bandwidth, the delays can become long enough to affect the ability to measure the range to the handset from the base station's antenna. More generally, a repeater or amplifier can have a similar impact on other parameters or characteristics of the wireless network or on the signals being transmitted. If the impacts of the amplifier, such as a delay introduced to a signal, are known by the base station, the amplifier's effects can be accounted for by the base station.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.